Ions of Eight Metals from Comet Dust Detected in Mars Atmosphere

These eight graphs present data from a mass spectrometer on NASA’s MAVEN orbiter identifying metal ions added to the Martian atmosphere shortly after comet C/2013 A1 Siding Spring sped close to Mars. MAVEN’s Neutral Gas and Ion Mass Spectrometer (NGIMS) directly samples the composition of Mars’ upper atmosphere when the spacecraft dips into the top of the atmosphere during each elongated orbit. These graphs show count rates of specific types of metal ions from each of multiple dips during the period from Oct. 18 to Oct. 23, 2014. The time of the comet’s closest approach to Mars is marked with a vertical line on each graph. Measurements were suspended temporarily around that time. The vertical axis is detector count rates, with different scales for the different types of metals. The pattern for each metal is similar: no detection in the days preceding the comet flyby, a sharp peak shortly after the flyby, then a rapid return to virtually no detections. The detected metals sodium and manganese each exist naturally as only one isotope. The detection charts include more than one isotope for nickel, magnesium, chromium, iron and zinc. Only one of potassium’s three isotopes was detected. The detection peaks resulted from dust particles that had been released by the comet’s nucleus vaporizing as they entered the Martian atmosphere at high speed. (Courtesy NASA/GSFC)